“One should have a general attitude of welcoming to everybody.”(From the “shot list” of the film, The Life and Times of Bertrand Russell, BBC TV, 1964 [ts., RA1 430 BBC])
Kenneth Blackwell

“I wish to propose for the reader’s favourable consideration a
doctrine which may, I fear, appear wildly paradoxical and
subversive. The doctrine in question is this: that it is undesirable
to believe a proposition when there is no ground whatever for
supposing it true.”
(From “Introduction: On the Value of Scepticism”, Sceptical Essays [London: Allen & Unwin, 1928])

“Supposing you got a crate of oranges that you opened, and you found all
the top layer of oranges bad, you would not argue, ‘The underneath ones
must be good, so as to redress the balance’; You would say, ‘Probably the
whole lot is a bad consignment’; and that is really what a scientific
person would say about the universe.”(From Why I Am Not a Christian [London: Watts, 1927])
Cosma Shalizi

“Probably in time physiologists will be able to make nerves
connecting the bodies of different people; this will have the
advantage that we shall be able to feel another man’s tooth
aching.”(From Human Knowledge [London: Allen & Unwin, 1948])
Lee Storey, who also contributed the following:

“A personality is an aggregate, or an organization, like a
cricket club. I can accept the dissolution of the MCC.”

“The secret of happiness is to face the fact that the world is horrible, horrible, horrible....”

“I don’t believe in meekness.”

“It is a waste of energy to be angry with a man who behaves badly,
just as it is to be angry with a car that won’t go.”

“Hatred of some sort is quite necessary—it needn’t be towards
people. But without some admixture of hatred one becomes soft and loses energy.”(All from Alan Wood, Bertrand Russell, the Passionate Sceptic [London: Allen & Unwin, 1957])

“The governors of the world believe, and have always believed, that virtue
can only be taught by teaching falsehood, and that any man who knew the
truth would be wicked. I disbelieve this, absolutely and entirely. I
believe that love of truth is the basis of all real virtue, and that virtues
based upon lies can only do harm.”(From The Prospects of Industrial Civilization [London: Allen & Unwin, 1923], p. 252; written in collaboration with Dora Russell)
Michael Rockler

“Truth is a shining goddess, always veiled, always distant, never wholly
approachable, but worthy of all the devotion of which the human spirit is capable.”(From “University Education”, Fact and Fiction [London: Allen & Unwin, 1961])
Thomas Daly

“Mathematics may be defined as the subject where we never know what we
are talking about, nor whether what we are saying is true.”(CPBR 3: 366 : 31-3 (“Recent Work on the Principles of Mathematics”,
a.k.a. “Mathematics and the Metaphysicians”)
Craig Burley

“... since one never knows what will be the line of advance, it is
always most rash to condemn what is not quite in the fashion of the moment.”(Review of MacColl’s Symbolic Logic and Its Applications, Mind, 15 [1906]: 260)
Paul Martin

“In very abstract studies such as philosophical logic, ...
the subject-matter that you are supposed to be thinking
of is so exceedingly difficult and elusive that any person
who has ever tried to think about it knows you do not
think about it except perhaps once in six months for half a
minute. The rest of the time you think about the symbols,
because they are tangible, for the thing you are supposed
to be thinking about is fearfully difficult and one does
not often manage to think about it. The really good philosopher
is the one who does once in six months think about it for a
minute. Bad philosophers never do.”(“The Philosophy of Logical Atomism”, Logic and Knowledge,
ed. R.C. Marsh (London: Allen & Unwin, 1956), p. 185)
Nino B. Cocchiarella

“Mathematics, rightly viewed, possesses not only
truth, but supreme beauty—a beauty cold and austere, like that of sculpture,
without appeal to any part of our weaker nature, without the gorgeous
trappings of painting or music, yet sublimely pure, and capable of a stern
perfection such as only the greatest art can show.”(“The Study of Mathematics”)

And for a nice, sobering (albeit non-contradictory) contrast try:

“... mathematics is only the art of saying the same thing in different words”(Autobiography, Vol. 3, penultimate par.)
Frank Smith (both); Thomas Drucker (1st only)

“I found one day in school a boy of medium size ill-treating a smaller
boy. I expostulated, but he replied: ’The bigs hit me, so I hit
the babies; that’s fair.’ In these words he epitomized the history
of the human race.”(Education and the Social Order [London: Allen & Unwin, 1932])
Tim Madigan

“United with his fellow-men by the strongest of all ties, the tie of a
common doom, the free man finds that a new vision is with him always,
shedding over every daily task the light of love. The life of Man is a
long march through the night, surrounded by invisible foes, tortured by
weariness and pain, towards a goal that few can hope to reach, and where
none may tarry long. One by one, as they march, our comrades vanish from
our sight, seized by the silent orders of omnipotent Death. Very brief is
the time in which we can help them, in which their happiness or misery is
decided. Be it ours to shed sunshine on their path, to lighten their
sorrows by the balm of sympathy, to give them the pure joy of a
never-tiring affection, to strengthen failing courage, to instil faith in
hours of despair. Let us not weigh in grudging scales their merits and
demerits, but let us think only of their need, of the sorrows, the
difficulties, perhaps the blindnesses, that make the misery of their lives;
let us remember that they are fellow-sufferers in the same darkness, actors
in the same tragedy with ourselves.”(“The Free Man’s Worship" [1903])
Dennis Darland